Neutrophils are a major contributor to the cellular damage that accompanies reperfusion of ischemic tissues. We propose to clone and produce through recombinant DNA methods a human protein that blocks attachment of neutrophils to endothelial cells in vivo and thereby prevents the entry of neutrophils into reperfused tissues and the consequent organ damage. This research will also lead to the development of a new technology for the treatment of a large class of human inflammatory diseases such as adult respiratory distress syndrome, irritable bowel disease, idiopathic pulmonary fibrosis, etc., in which neutrophils appear to play a destructive role. In Phase I, we will immunize mice and select for monoclonal antibodies that react with the protein, using an in vitro functional assay. These monoclonals will be used to identify the protein on Western blots and in immunoprecipitation experiments. In Phase II, we will use the monoclonal antibodies to purify enough of the protein to determine a partial amino-acid sequence. Oligonucleotides corresponding to the determined amino-acid sequence and/or the monoclonal antibodies will be used to isolate a cDNA encoding the protein form a cDNA expression library. The protein will be produced in large quantities through recombinant DNA methods to evaluate its effectiveness in vitro and in vivo for preventing attachment of the neutrophils to endothelial cells and consequent damage to reperfused tissues.